Preface
Please take time to carefully read and understand the
following instructions before you install or attempt to oper-
ate this equipment. Becoming familiar with the product
and its correct operating procedures will help assure you of
maximum musical enjoyment and reliable operation. The
effort you invest now will be well rewarded in the years
ahead
Packaging
Save all packaging accompanying this product. You have
purchased a precision electronic instrument, and it should
be properly cartoned any time shipment becomes neces-
sary. It is very possible that this unit could be damaged
during shipment if repackaged in cartoning other than that
designed for it. The original packaging materials help pro-
tect your investment from unnecessary damage, delay and
added expense whenever shipment of this unit is required.
Accessories
1 – Phillips head screwdriver for cover removal
1 – Plastic screwdriver for bias adjustments
User replaceable spare fuses include:
1 – 8 Amp MDL slo-blo with 120V units or 100V units
1 – T4A 250V slo-blo with 220V/240V units
Warnings
1
. Do not touch hot tubes. Keep away from children.
2
. To prevent fire or shock hazard, do not expose your
HD220 to rain or moisture.
3
.
This unit contains voltages which can cause serious
injury or death. Do not operate with covers removed.
Refer servicing to your authorized Audio Research dealer
or other qualified personnel.
4
. The 12-gauge, 3-conductor detachable power cord on
your HD220 is equipped with a standard 3-prong
grounding plug. If used normally, it will provide a safe
earth ground connection of the chassis. Refer to the
section on “AC Power Connections” for detailed
information.
5
. For continued protection against fire hazard,
replace fuses only with the same type and rating of fuses
as specified.
Warning!
Read Owner's Manual before installing or operating
this product!
Do not attempt to install or remove any vacuum
tubes unless this unit is turned off and disconnected
from the A.C. power outlet. Unit should be connect-
ed to the A.C. outlet and turned on only after all
vacuum tubes have been installed and appropriate
pa nels have be en repla ced and faste ne d. Se e
owner's manual for installation instructions.
Before replacing vacuum tubes, turn off unit, discon-
nect from A.C. outlet and allow installed tubes to
cool before attempting to remove them. Hot tubes
may cause burns or other injury if not allowed to
cool before removal.
When removing or installing tubes, do not touch tube
socket contacts or other components as the circuit
may retain sufficient levels of voltage and current to
cause injury or death.
Contact your dealer or Audio Research Customer
Service (763-577-9700) if you have any questions
about installing or replacing vacuum tubes in this
unit.
Model HD220
DO NOT ATTEMPT TO OPERATE THIS
EQUIPMENT BEFORE INSTALLING THE NUMBERED
VACUUM TUBES IN THEIR RESPECTIVE SOCKETS.
R E A R
F R O N T
V 4
V 1
V 2
V 3
6H30
6922
TUBE LOCATIONS
TOP VIE W
1
6H30
–( T a l l er)–
– (Sh o r t er) –
6922
